Step 1

In a large saucepan over medium high heat, combine the chicken meat, chicken broth, salt and pepper. Bring to a boil and reduce heat to low. Cover and let simmer for 30 minutes, or until chicken is no longer pink in the center and the juices run clear.

Step 2

Remove the chicken and let cool. Pour the remaining chicken broth mixture into a measuring cup. Let stand; spoon off fat. Add enough milk to the broth mixture to equal 2 1/2 cups. Cut chicken into 1/2 inch pieces.

Step 3

In the same pan, melt butter or margarine over medium heat. Add the onion and celery. Saute, stirring, for 3 minutes. Stir in flour until well blended. Gradually stir in broth mixture. Simmer, stirring constantly, until the sauce thickens and boils. Add the chicken, vegetables, parsley and thyme. Pour mixture into a 1 1/2 quart deep casserole dish.

Step 4

Preheat oven to 400 degrees F (200 degrees C).

Step 5

Roll out pastry 1 inch larger than the diameter of the casserole dish on a lightly floured surface. Cut slits in the pastry for venting air. Place pastry on top of casserole. Roll edges and cut away extra pastry; flute edges by pinching together. Reroll scraps to cut into decorative designs. Place on top of pastry. Brush pastry with beaten egg and bake in the preheated oven for 30 minutes or until the crust is golden brown and the filling is bubbling. Let cool for 10 minutes and serve.